The invention relates to the production of acetylated aromatic compounds using a palladium catalyst.
The palladium-catalyzed vinylation of organic halides has been reviewed by Heck, Organic Reactions, vol. 27 (1982), beginning at page 345. Process conditions, recited at page 360, do not require the use of a solvent, although an organic amine can apparently function as a solvent. Other solvents used heretofore include acetonitrile, methanol, dimethylformamide, N-methylpyrrolidinone, and hexamethylphosphoramide.
Heck, U.S. Pat. No. 3,922,299, incorporated herein by reference, teaches that the reaction can be carried out with or without a solvent. Suggested solvents include acetonitrile, tetrahydrofuran, or excess olefin.
The Heck vinylation reaction has been used to vinylate various kinds of compounds, including the use of alkyl vinyl ethers to vinylate aryl compounds. For instance, Hallberg et al. in "Palladium-Catalyzed Arylation of Methyl Vinyl Ether," J. Org. Chem., vol. 46, 5414-15 (1981), disclose that 4-nitrohalobenzenes can be reacted with methyl vinyl ether in the presence of a palladium catalyst to form a variety of products. On page 5415, Hallberg et al. disclose that the reaction of 4-iodoanisole with methyl vinyl ether in the presence of triethylamine yields an acetophenone product after work up with 10 percent aqueous hydrochloric acid. The reference is silent as to water and inorganic hydrogen halide acceptors.
In addition, Andersson et al. in "Synthesis of .beta.-Arylvinyl Ethers by the Palladium-Catalyzed Reaction of Aryl Chlorides with Vinyl Ethers," J. Org. Chem., vol. 53, 235-239 (1988), disclose reactions as defined in the title of the article. A vinylically unsaturated product is reported as the major product in every case except in the case of the reaction of anisole. The reference is silent as to water, inorganic hydrogen halide acceptors, and halogenated benzocyclobutenes. In the examples, it is noted that acid work-up produces an acetophenone from the .alpha.-isomer.
Also, Arai et al. in "Palladium-Catalyzed Phenylation of Enol Ethers and Acetates," J. Org. Chem., vol. 44, 21-23 (1979), report the title reactions using triethylamine in the absence of water as a solvent. The reported products are vinyl ethers.
Andersson et al. in "Chelation-Controlled, Palladium-Catalyzed Vinylic Substitution Reactions of Vinyl Ethers. 2-Arylethanal Equivalents from Aryl Halides," J. Org. Chem., vol. 55, 5757-5761 (1990), report the production of several vinyl aryl ethers as shown in Table II at page 5759. Dipotassium carbonate is disclosed as the base. Water is not added to the reaction mixture.
Additionally, Andersson et al. in "Regiochemistry of Palladium-Catalyzed Arylation Reactions of Enol Ethers. Electronic Control of Selection for .alpha.- or .beta.-Arylation," J. Org. Chem., vol. 52, 3529-3536 (1987), report arylation of vinyl alkyl ethers using palladium catalysts. .alpha.-Arylation is favored if a triphenylphosphine ligand and acetonitrile is used.
It is noted that Lloyd et al. in "The Electrophilic Substitution of Benzocyclobutene-I," Tetrahedron, vol. 20, 2185-2194 (1964), report that nitration, Friedal-Crafts acetylation, and hydrobromination of benzocyclobutene produce predominately ring opened products.
These references, however, do not disclose a one step process for making actyl products using Heck type chemistry.